Green tea steeped from whole tea leaves, not bags, contains a substantial amount of potent anti-oxidants, an amino acid called l-theanine, and a moderate amount of caffeine in a form which is less bioactive than that found in coffee or the synthetic stuff added to beverages. The anti-oxidant's help mitigate the cellular damage caused by excess oxidative stress, which can take place with greater intensity during episodes of mania or prolonged periods of anxiety.

L-Theanine has some anxiolytic properties as well as being neuroprotective against excess glutamate. Mood stabilizers reduce excess glutamate as well. Excess glutamate causes cellular damage which when out of control can even lead to neuronal cell death. The caffeine and theanine have a synergistic interaction, improving focus while reducing the stimulatory effects. The result being that green tea promotes a state of calm attentiveness as opposed to the wired feeling from coffee.

I think that pdoc spent some time learning information many clinicians are oblivious to.